uint64_t wallet2::get_approximate_blockchain_height() const
{
  // time of v2 fork
  const time_t fork_time = m_nettype == TESTNET ? 1448285909 : m_nettype == STAGENET ? 1520937818 : 1458748658;
  // v2 fork block
  const uint64_t fork_block = m_nettype == TESTNET ? 624634 : m_nettype == STAGENET ? 32000 : 1009827;
  // avg seconds per block
  const int seconds_per_block = DIFFICULTY_TARGET_V2;
  // Calculated blockchain height
  uint64_t approx_blockchain_height = fork_block + (time(NULL) - fork_time)/seconds_per_block;
  // testnet got some huge rollbacks, so the estimation is way off
  static const uint64_t approximate_testnet_rolled_back_blocks = 303967;
  if (m_nettype == TESTNET && approx_blockchain_height > approximate_testnet_rolled_back_blocks)
    approx_blockchain_height -= approximate_testnet_rolled_back_blocks;
  LOG_PRINT_L2("Calculated blockchain height: " << approx_blockchain_height);
  return approx_blockchain_height;